A basic introduction on how to read the eventAnalysis files to perform an analysis

Reading eventAnalysis Output Files

Some sample macros can be found in the macros directory. Extensive use is made of analysisUtilityToolsLibrary, written in C++.

Using The Browser

For first time users, the Browser (do TBrowser b; after opening a file in ROOT) is probably the best way to investigate what is contained in the output trees. This is not how you would do an analysis, but it will give you an idea what is there.

All eventAnalysis output that is saved in the trees must be browsable.

ccqeAnalysis.py is an example of using Python to look at analysis files and create histograms etc. It can be copied and changed to provide a template for a user analysis.

Being written in python, it is extremely easy to access the objects saved in the eventAnalysis files, while at the same time PyROOT is used to make all the ROOT classes directly available. See eventAnalysisReadoutScripts for more details

runAnalysis.py runs such analysis files.

./runAnalyses.py –help will print out a usage message:

Usage: runAnalyses.py [options] files
       When successful, always writes a file "eventAnalysisReadInit.C", which
       can be executed in ROOT to manually initialise it for browsing eventAnalysis
       files (but not when just showing the help message).

Options:
  -h, --help      show this help message and exit
  -nNEVENTS       Set the number of events to process. Default is
                  1000000000.
  -sNSKIP         Set the number of events to skip. Default is 0.
  -aANALYSISNAME  Set the analysis script to read (analysisName.py) and
                  the  default output name (analysisName.root). The
                  latter can be overridden with the -o option. The
                  default analysisName is 'ccqeAnalysis'.
  --neut          Force code to assume NEUT as the interaction generator.
  --genie         Force code to assume GENIE as the interaction
                  generator. By default the generator names use the file
                  catalogue, or are guessed.
  --nuance        Force code to assume NUANCE as the interaction
                  generator. By default the generator names use the file
                  catalogue, or are guessed.
  -oOUTPUT        Set output file, overriding analysisName.root.
  -c              Compile the C++ macros for use by ROOT macros. An input
                  eventAnalysis file needs to be specified. Not needed when
                  using the python-based analyses because compilation is
                  automatic.
  --noisyROOT     Show all ROOT standard output, including those that are
                  unnecessary and often misleading in normal usage.

If the readout library libReadeventAnalysis/libReadeventAnalysis.so does not exist, it uses the first input file specified to create and compile the library.

If you have errors related to libReadeventAnalysis, it might be a good idea to remove the libReadeventAnalysis directory and try again.

The specifics of the analysis are contained in a separate file, which by default is ccqeAnalysis.py. The -a option allows one to choose this name.

Sets up the eventChain, and loads headers as listed at the top of the external analysis file.

Python analyses with C++ utility scripts appear to run fast enough to be used for large-scale analyses.

(This is very much a condensed overview showing where to look when trying to read out the eventAnalysis files. For more in-depth documentation, go to analysisUtilityToolsLibrary eventAnalysisReadoutScripts and howTheReadOutLibrariesAreCompiled)